diversity Article Beyond Endocasts: Using Predicted Brain-Structure Volumes of Extinct Birds to Assess Neuroanatomical and Behavioral Inferences 1, , 2 2 Catherine M. Early * y , Ryan C. Ridgely and Lawrence M. Witmer 1 Department of Biological Sciences, Ohio University, Athens, OH 45701, USA 2 Department of Biomedical Sciences, Heritage College of Osteopathic Medicine, Ohio University, Athens, OH 45701, USA;
[email protected] (R.C.R.);
[email protected] (L.M.W.) * Correspondence:
[email protected] Current Address: Florida Museum of Natural History, University of Florida, Gainesville, FL 32611, USA. y Received: 1 November 2019; Accepted: 30 December 2019; Published: 17 January 2020 Abstract: The shape of the brain influences skull morphology in birds, and both traits are driven by phylogenetic and functional constraints. Studies on avian cranial and neuroanatomical evolution are strengthened by data on extinct birds, but complete, 3D-preserved vertebrate brains are not known from the fossil record, so brain endocasts often serve as proxies. Recent work on extant birds shows that the Wulst and optic lobe faithfully represent the size of their underlying brain structures, both of which are involved in avian visual pathways. The endocasts of seven extinct birds were generated from microCT scans of their skulls to add to an existing sample of endocasts of extant birds, and the surface areas of their Wulsts and optic lobes were measured. A phylogenetic prediction method based on Bayesian inference was used to calculate the volumes of the brain structures of these extinct birds based on the surface areas of their overlying endocast structures. This analysis resulted in hyperpallium volumes of five of these extinct birds and optic tectum volumes of all seven extinct birds.